Journal of the Physical Society of Japan, Aug 15, 1993
Optical properties of fcc C 60 samples have been studied by using photoacoustic spectroscopy over... more Optical properties of fcc C 60 samples have been studied by using photoacoustic spectroscopy over the temperature range 30–300 K. A sharp absorption edge is seen at 1.7 eV at room temperature. The optical absorption spectrum changes drastically at 80 K. Another change of absorption spectrum is also observed at 260 K. These changes can be explained by the molecular motion of C 60 .
Carbon nanofiber (CNF) aerogels are a new class of advanced materials that have many potential ap... more Carbon nanofiber (CNF) aerogels are a new class of advanced materials that have many potential applications in the energy and environmental sectors. However, some CNF aerogels consist of materials derived from fossil-fuels and energy-intensive production processes. For the successful industryscale applications of carbon aerogels, the development of large-scale production methods with a smaller environmental footprint is required. Cellulose is a promising alternative material as a precursor of CNF aerogels, due to its renewability, high carbon content, and carbon neutrality. However, the low yield of CNF aerogels from the pyrolysis of cellulose nanofiber (CellNF) aerogels hinders their practical applications. To increase the yield of CNF aerogels from the pyrolysis of CellNF aerogels, we investigated the use of ammonium chloride (NH 4 Cl) as a carbonization promoter. The influence of the amount of NH 4 Cl, pyrolysis temperature, and method of adding NH 4 Cl to the cellulose precursor were systematically studied. Drastic improvements were observed in the yields of CNF aerogels, by 141-446% at 600°C and 118-225% at 800°C of pyrolysis, with the addition of NH 4 Cl (0.5-1.5 NH 4 Cl/CellNF weight ratio). The morphology, chemical and crystalline characteristics, microstructure, and porosity of CNFs in the aerogels were not affected by the addition of NH 4 Cl.
Photoacoustic spectroscopy measurements have been carried out on the Se-ring microclusters confin... more Photoacoustic spectroscopy measurements have been carried out on the Se-ring microclusters confined in the cages of zeolite 4A. The shift of photoabsorption edge and the new absorption bands around 1.5 and 1.9 eV appeared by illumination of the light having the band-gap energy at low temperature. These phenomena may be associated with the distortion of Se ring and the formation of dangling bonds. Mixing of S or Te to the Se microclusters causes appreciable change in the photoinduced phenomena.
Widely known for its recreational use, the cannabis plant also has the potential to act as an ant... more Widely known for its recreational use, the cannabis plant also has the potential to act as an antibacterial agent in the medicinal field. The analysis of cannabis plants/products in both pharmacological and forensic studies often requires the separation of compounds of interest and/or accurate identification of the whole cannabinoid profile. In order to provide a complete separation and detection of cannabinoids, a new two-dimensional liquid chromatography method has been developed using acidic potassium permanganate chemiluminescence detection, which has been shown to be selective for cannabinoids. This was carried out using a Luna 100 Å CN column and a Poroshell 120 EC-C 18 column in the first and second dimensions, respectively. The method has utilized a large amount of the available separation space with a spreading angle of 48.4Њ and a correlation of 0.66 allowing the determination of more than 120 constituents and mass spectral identification of ten cannabinoids in a single analytical run. The method has the potential to improve research involved in the characterization of sensitive, complex matrices.
This is a collection of selected, peer reviewed papers from the International Conference on Nanom... more This is a collection of selected, peer reviewed papers from the International Conference on Nanomaterials: Science, Technology and Applications (ICM' 13), December 5-7, 2013, Chennai, India. The 54 papers are grouped as follows: Nano Materials: Synthesis and Characterisation, Electrical, Magnetic, Optical Properties of Nanomaterials, Polymers and Nanocomposites, Bio Nanomaterials and their Applications, Nanomaterials: Energy & Environment, and, Nanomaterials: Theoretical and Computational Studies.
... for chalcogen Correspondence to: Professor H. Endo, Department of Physics, Faculty of Science... more ... for chalcogen Correspondence to: Professor H. Endo, Department of Physics, Faculty of Science, Kyoto University, Oiwake-cho, Kitasira: kawa, Sakyo-cho ... A theoretical study by Ikawa and Fukutome has revealed that, near the chain end, chalcogen chains tend to have a planar ...
Journal of Colloid and Interface Science, Feb 1, 2022
Highlights • Magnetic chitosan-palygorskite (MCP) was fabricated in simple and green method. • MC... more Highlights • Magnetic chitosan-palygorskite (MCP) was fabricated in simple and green method. • MCP removed 58.5 mg g-1 of lead from water. • Complexation and chemical reduction of lead on MCP surface was evidenced. • MCP recorded 82% lead removal even following four regeneration cycles. • MCP retained superparamagnetic nature after regeneration.
EXAFS measurements have been carried out on Se K-edge and Te K-edge for Se8-x Te x and Se8-x S x ... more EXAFS measurements have been carried out on Se K-edge and Te K-edge for Se8-x Te x and Se8-x S x microclusters with 8 chalcogen atoms. The clusters with various compositions were isolated in a synthetic 4A zeolite which has 11Å-diameter cage units. The data analysis led us to believe that the clusters form 8-membered rings in the cage. In Se8-x Te x microclusters, Se–Se bonds and Te–Te bonds are shorter than those in the crystalline state. It is found that Se–Te unlike-pairs are preferred over Se–Se and Te–Te like pairs. On the other hand, in Se8-x S x microclusters, Se–Se and S–S like-pairs are found to be preferred over Se–S unlike-pairs.
Ce0.80Pr0.12Sn0.08O2−δ combination catalyst exhibited highest CO oxidation activity owing to its ... more Ce0.80Pr0.12Sn0.08O2−δ combination catalyst exhibited highest CO oxidation activity owing to its high specific surface area, better reducibility, superior surface active oxygen species, and oxygen vacancies among various samples investigated.
The temperature and pressure variations of optical reflectivity of Se,-,Te, have been measured in... more The temperature and pressure variations of optical reflectivity of Se,-,Te, have been measured in the energy range between 0.5 and 4.2 eV. In liquid Te, a bkoad peak appears around 2 eV, and a Drude term is evident at low photon energy region, suggesting that the liquid Te has a metallic nature. At high temperature and pressure, all the mixtures become metallic. For liquid Te positive magnetoresistance Ap/p is observed, and the two temperature ranges are distinguished in the temperature variation of A p/p, including the supercooled state.
The authors maintain a culture collection of over 2,500 cyanobacteria and photosynthetic bacteria... more The authors maintain a culture collection of over 2,500 cyanobacteria and photosynthetic bacteria and 2,000 eukaryotic algae for research on H{sub 2} biophotoproduction as well as other projects. A high H{sub 2}-producing strain Synechococcus sp. Miami BG 043511 from the collection has been used to examine H{sub 2} production in relation to water photolysis and substance degradation, high O{sub 2}-tolerance characterization of nitrogenase, and interactive effects of light intensity and cell density on H{sub 2} production and its stable isotope fractionation. When cellular carbohydrate is depleted, no H{sub 2} production occurs. However, when pyruvate or glucose is added, H{sub 2} production begins. On the other hand, when glucose and DCMU are added to cellular carbohydrate-depleted cells from synchronous cultures, H{sub 2} production is inhibited compared with that with glucose addition alone. These results indicate that water photolysis alone cannot directly induce H{sub 2} product...
To develop efficient materials for CO oxidation, a series of co-doped CeO₂ ternary oxide solid so... more To develop efficient materials for CO oxidation, a series of co-doped CeO₂ ternary oxide solid solutions (Ce₀.₈₀M₀.₁₂Sn₀.₀₈O₂₋δ, M = Hf, Zr, Pr, and La) were prepared by a simple coprecipitation method. The fundamental characteristics of the co-doped CeO₂ samples were studied by X-ray diffraction, Raman spectroscopy, UV-visible diffuse reflectance spectroscopy, transmission electron microscopy, Brunauer–Emmett–Teller surface area, H₂-temperature programmed reduction, X-ray photoelectron spectroscopy, and O₂-temperature programmed desorption. The oxidation of CO was chosen as a model reaction to evaluate the catalytic performance of these samples. The characterization results revealed that ternary oxide solid solutions had significantly enhanced surface area, improved reducibility, increased oxygen mobility and higher quantity of surface adsorbed oxygen species and oxygen vacancies, compared to undoped CeO₂. The CO oxidation performance of CeO₂ was greatly improved upon co-doping due...
Highlights • Magnetic chitosan-palygorskite (MCP) was fabricated in simple and green method. • MC... more Highlights • Magnetic chitosan-palygorskite (MCP) was fabricated in simple and green method. • MCP removed 58.5 mg g-1 of lead from water. • Complexation and chemical reduction of lead on MCP surface was evidenced. • MCP recorded 82% lead removal even following four regeneration cycles. • MCP retained superparamagnetic nature after regeneration.
Nanomedicine has seen a significant rise in the development of new research tools and clinically ... more Nanomedicine has seen a significant rise in the development of new research tools and clinically functional devices. In this regard, significant advances and new commercial applications are expected in the pharmaceutical and orthopedic industries. For advanced orthopedic implant technologies, appropriate nanoscale surface modifications are highly effective strategies and are widely studied in the literature for improving implant performance. It is well-established that implants with nanotubular surfaces show a drastic improvement in new bone creation and gene expression compared to implants without nanotopography. Nevertheless, the scientific and clinical understanding of mixed oxide nanotubes (MONs) and their potential applications, especially in biomedical applications are still in the early stages of development. This review aims to establish a credible platform for the current and future roles of MONs in nanomedicine, particularly in advanced orthopedic implants. We first introduce the concept of MONs and then discuss the preparation strategies. This is followed by a review of the recent advancement of MONs in biomedical applications, including mineralization abilities, biocompatibility, antibacterial activity, cell culture, and animal testing, as well as clinical possibilities. To conclude, we propose that the combination of nanotubular surface modification with incorporating sensor allows clinicians to precisely record patient data as a critical contributor to evidence-based medicine.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Carbon nanofiber (CNF) aerogels are a new class of advanced materials that have many potential ap... more Carbon nanofiber (CNF) aerogels are a new class of advanced materials that have many potential applications in the energy and environmental sectors. However, some CNF aerogels consist of materials derived from fossil-fuels and energy-intensive production processes. For the successful industryscale applications of carbon aerogels, the development of large-scale production methods with a smaller environmental footprint is required. Cellulose is a promising alternative material as a precursor of CNF aerogels, due to its renewability, high carbon content, and carbon neutrality. However, the low yield of CNF aerogels from the pyrolysis of cellulose nanofiber (CellNF) aerogels hinders their practical applications. To increase the yield of CNF aerogels from the pyrolysis of CellNF aerogels, we investigated the use of ammonium chloride (NH 4 Cl) as a carbonization promoter. The influence of the amount of NH 4 Cl, pyrolysis temperature, and method of adding NH 4 Cl to the cellulose precursor were systematically studied. Drastic improvements were observed in the yields of CNF aerogels, by 141-446% at 600°C and 118-225% at 800°C of pyrolysis, with the addition of NH 4 Cl (0.5-1.5 NH 4 Cl/CellNF weight ratio). The morphology, chemical and crystalline characteristics, microstructure, and porosity of CNFs in the aerogels were not affected by the addition of NH 4 Cl.
This study examines the suspension stability of iron oxide nanoparticles of different sizes, magn... more This study examines the suspension stability of iron oxide nanoparticles of different sizes, magnetic susceptibility, and saturation magnetization over long time scales in dilute systems using timeresolved UV-visible spectroscopy. The effects of citric acid as a chelating agent and applied external magnetic field are also studied. UV-visible spectra are obtained at different times for citric-acid-stabilized nanoparticles dispersed in water, and the peak absorbance is tracked with time, in the presence and absence of external magnetic fields. It is seen that the nanoparticles sediment slowly even in the absence of chain formation, with the phenomenon occurring in two-to-three regimes for the systems studied. Sedimentation exhibits either exponential or powerlaw behavior of maximum absorbance with time. In the dilute dispersions studied, thermal dispersion is about two orders of magnitude stronger than van der Waals interactions, and chain formation is not easy. Yet, it is likely that local anisotropic structures of the nanoparticles form, through which the attractive interactions result in sedimentation. Citric acid gradually stabilizes the aggregating particles; after an initial faster sedimentation, electrostatic repulsion causes the particles to segregate, as observed by a linear increase in the concentration of the nanoparticles at long times. In the presence of magnetic field, stabilization effects are significantly reduced. It is seen that though the attractive force between the nanoparticles and the external field is smaller than Brownian forces, together with van der Waals interactions, these Electronic supplementary material The online version of this article (
Journal of the Physical Society of Japan, Aug 15, 1993
Optical properties of fcc C 60 samples have been studied by using photoacoustic spectroscopy over... more Optical properties of fcc C 60 samples have been studied by using photoacoustic spectroscopy over the temperature range 30–300 K. A sharp absorption edge is seen at 1.7 eV at room temperature. The optical absorption spectrum changes drastically at 80 K. Another change of absorption spectrum is also observed at 260 K. These changes can be explained by the molecular motion of C 60 .
Carbon nanofiber (CNF) aerogels are a new class of advanced materials that have many potential ap... more Carbon nanofiber (CNF) aerogels are a new class of advanced materials that have many potential applications in the energy and environmental sectors. However, some CNF aerogels consist of materials derived from fossil-fuels and energy-intensive production processes. For the successful industryscale applications of carbon aerogels, the development of large-scale production methods with a smaller environmental footprint is required. Cellulose is a promising alternative material as a precursor of CNF aerogels, due to its renewability, high carbon content, and carbon neutrality. However, the low yield of CNF aerogels from the pyrolysis of cellulose nanofiber (CellNF) aerogels hinders their practical applications. To increase the yield of CNF aerogels from the pyrolysis of CellNF aerogels, we investigated the use of ammonium chloride (NH 4 Cl) as a carbonization promoter. The influence of the amount of NH 4 Cl, pyrolysis temperature, and method of adding NH 4 Cl to the cellulose precursor were systematically studied. Drastic improvements were observed in the yields of CNF aerogels, by 141-446% at 600°C and 118-225% at 800°C of pyrolysis, with the addition of NH 4 Cl (0.5-1.5 NH 4 Cl/CellNF weight ratio). The morphology, chemical and crystalline characteristics, microstructure, and porosity of CNFs in the aerogels were not affected by the addition of NH 4 Cl.
Photoacoustic spectroscopy measurements have been carried out on the Se-ring microclusters confin... more Photoacoustic spectroscopy measurements have been carried out on the Se-ring microclusters confined in the cages of zeolite 4A. The shift of photoabsorption edge and the new absorption bands around 1.5 and 1.9 eV appeared by illumination of the light having the band-gap energy at low temperature. These phenomena may be associated with the distortion of Se ring and the formation of dangling bonds. Mixing of S or Te to the Se microclusters causes appreciable change in the photoinduced phenomena.
Widely known for its recreational use, the cannabis plant also has the potential to act as an ant... more Widely known for its recreational use, the cannabis plant also has the potential to act as an antibacterial agent in the medicinal field. The analysis of cannabis plants/products in both pharmacological and forensic studies often requires the separation of compounds of interest and/or accurate identification of the whole cannabinoid profile. In order to provide a complete separation and detection of cannabinoids, a new two-dimensional liquid chromatography method has been developed using acidic potassium permanganate chemiluminescence detection, which has been shown to be selective for cannabinoids. This was carried out using a Luna 100 Å CN column and a Poroshell 120 EC-C 18 column in the first and second dimensions, respectively. The method has utilized a large amount of the available separation space with a spreading angle of 48.4Њ and a correlation of 0.66 allowing the determination of more than 120 constituents and mass spectral identification of ten cannabinoids in a single analytical run. The method has the potential to improve research involved in the characterization of sensitive, complex matrices.
This is a collection of selected, peer reviewed papers from the International Conference on Nanom... more This is a collection of selected, peer reviewed papers from the International Conference on Nanomaterials: Science, Technology and Applications (ICM' 13), December 5-7, 2013, Chennai, India. The 54 papers are grouped as follows: Nano Materials: Synthesis and Characterisation, Electrical, Magnetic, Optical Properties of Nanomaterials, Polymers and Nanocomposites, Bio Nanomaterials and their Applications, Nanomaterials: Energy & Environment, and, Nanomaterials: Theoretical and Computational Studies.
... for chalcogen Correspondence to: Professor H. Endo, Department of Physics, Faculty of Science... more ... for chalcogen Correspondence to: Professor H. Endo, Department of Physics, Faculty of Science, Kyoto University, Oiwake-cho, Kitasira: kawa, Sakyo-cho ... A theoretical study by Ikawa and Fukutome has revealed that, near the chain end, chalcogen chains tend to have a planar ...
Journal of Colloid and Interface Science, Feb 1, 2022
Highlights • Magnetic chitosan-palygorskite (MCP) was fabricated in simple and green method. • MC... more Highlights • Magnetic chitosan-palygorskite (MCP) was fabricated in simple and green method. • MCP removed 58.5 mg g-1 of lead from water. • Complexation and chemical reduction of lead on MCP surface was evidenced. • MCP recorded 82% lead removal even following four regeneration cycles. • MCP retained superparamagnetic nature after regeneration.
EXAFS measurements have been carried out on Se K-edge and Te K-edge for Se8-x Te x and Se8-x S x ... more EXAFS measurements have been carried out on Se K-edge and Te K-edge for Se8-x Te x and Se8-x S x microclusters with 8 chalcogen atoms. The clusters with various compositions were isolated in a synthetic 4A zeolite which has 11Å-diameter cage units. The data analysis led us to believe that the clusters form 8-membered rings in the cage. In Se8-x Te x microclusters, Se–Se bonds and Te–Te bonds are shorter than those in the crystalline state. It is found that Se–Te unlike-pairs are preferred over Se–Se and Te–Te like pairs. On the other hand, in Se8-x S x microclusters, Se–Se and S–S like-pairs are found to be preferred over Se–S unlike-pairs.
Ce0.80Pr0.12Sn0.08O2−δ combination catalyst exhibited highest CO oxidation activity owing to its ... more Ce0.80Pr0.12Sn0.08O2−δ combination catalyst exhibited highest CO oxidation activity owing to its high specific surface area, better reducibility, superior surface active oxygen species, and oxygen vacancies among various samples investigated.
The temperature and pressure variations of optical reflectivity of Se,-,Te, have been measured in... more The temperature and pressure variations of optical reflectivity of Se,-,Te, have been measured in the energy range between 0.5 and 4.2 eV. In liquid Te, a bkoad peak appears around 2 eV, and a Drude term is evident at low photon energy region, suggesting that the liquid Te has a metallic nature. At high temperature and pressure, all the mixtures become metallic. For liquid Te positive magnetoresistance Ap/p is observed, and the two temperature ranges are distinguished in the temperature variation of A p/p, including the supercooled state.
The authors maintain a culture collection of over 2,500 cyanobacteria and photosynthetic bacteria... more The authors maintain a culture collection of over 2,500 cyanobacteria and photosynthetic bacteria and 2,000 eukaryotic algae for research on H{sub 2} biophotoproduction as well as other projects. A high H{sub 2}-producing strain Synechococcus sp. Miami BG 043511 from the collection has been used to examine H{sub 2} production in relation to water photolysis and substance degradation, high O{sub 2}-tolerance characterization of nitrogenase, and interactive effects of light intensity and cell density on H{sub 2} production and its stable isotope fractionation. When cellular carbohydrate is depleted, no H{sub 2} production occurs. However, when pyruvate or glucose is added, H{sub 2} production begins. On the other hand, when glucose and DCMU are added to cellular carbohydrate-depleted cells from synchronous cultures, H{sub 2} production is inhibited compared with that with glucose addition alone. These results indicate that water photolysis alone cannot directly induce H{sub 2} product...
To develop efficient materials for CO oxidation, a series of co-doped CeO₂ ternary oxide solid so... more To develop efficient materials for CO oxidation, a series of co-doped CeO₂ ternary oxide solid solutions (Ce₀.₈₀M₀.₁₂Sn₀.₀₈O₂₋δ, M = Hf, Zr, Pr, and La) were prepared by a simple coprecipitation method. The fundamental characteristics of the co-doped CeO₂ samples were studied by X-ray diffraction, Raman spectroscopy, UV-visible diffuse reflectance spectroscopy, transmission electron microscopy, Brunauer–Emmett–Teller surface area, H₂-temperature programmed reduction, X-ray photoelectron spectroscopy, and O₂-temperature programmed desorption. The oxidation of CO was chosen as a model reaction to evaluate the catalytic performance of these samples. The characterization results revealed that ternary oxide solid solutions had significantly enhanced surface area, improved reducibility, increased oxygen mobility and higher quantity of surface adsorbed oxygen species and oxygen vacancies, compared to undoped CeO₂. The CO oxidation performance of CeO₂ was greatly improved upon co-doping due...
Highlights • Magnetic chitosan-palygorskite (MCP) was fabricated in simple and green method. • MC... more Highlights • Magnetic chitosan-palygorskite (MCP) was fabricated in simple and green method. • MCP removed 58.5 mg g-1 of lead from water. • Complexation and chemical reduction of lead on MCP surface was evidenced. • MCP recorded 82% lead removal even following four regeneration cycles. • MCP retained superparamagnetic nature after regeneration.
Nanomedicine has seen a significant rise in the development of new research tools and clinically ... more Nanomedicine has seen a significant rise in the development of new research tools and clinically functional devices. In this regard, significant advances and new commercial applications are expected in the pharmaceutical and orthopedic industries. For advanced orthopedic implant technologies, appropriate nanoscale surface modifications are highly effective strategies and are widely studied in the literature for improving implant performance. It is well-established that implants with nanotubular surfaces show a drastic improvement in new bone creation and gene expression compared to implants without nanotopography. Nevertheless, the scientific and clinical understanding of mixed oxide nanotubes (MONs) and their potential applications, especially in biomedical applications are still in the early stages of development. This review aims to establish a credible platform for the current and future roles of MONs in nanomedicine, particularly in advanced orthopedic implants. We first introduce the concept of MONs and then discuss the preparation strategies. This is followed by a review of the recent advancement of MONs in biomedical applications, including mineralization abilities, biocompatibility, antibacterial activity, cell culture, and animal testing, as well as clinical possibilities. To conclude, we propose that the combination of nanotubular surface modification with incorporating sensor allows clinicians to precisely record patient data as a critical contributor to evidence-based medicine.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Carbon nanofiber (CNF) aerogels are a new class of advanced materials that have many potential ap... more Carbon nanofiber (CNF) aerogels are a new class of advanced materials that have many potential applications in the energy and environmental sectors. However, some CNF aerogels consist of materials derived from fossil-fuels and energy-intensive production processes. For the successful industryscale applications of carbon aerogels, the development of large-scale production methods with a smaller environmental footprint is required. Cellulose is a promising alternative material as a precursor of CNF aerogels, due to its renewability, high carbon content, and carbon neutrality. However, the low yield of CNF aerogels from the pyrolysis of cellulose nanofiber (CellNF) aerogels hinders their practical applications. To increase the yield of CNF aerogels from the pyrolysis of CellNF aerogels, we investigated the use of ammonium chloride (NH 4 Cl) as a carbonization promoter. The influence of the amount of NH 4 Cl, pyrolysis temperature, and method of adding NH 4 Cl to the cellulose precursor were systematically studied. Drastic improvements were observed in the yields of CNF aerogels, by 141-446% at 600°C and 118-225% at 800°C of pyrolysis, with the addition of NH 4 Cl (0.5-1.5 NH 4 Cl/CellNF weight ratio). The morphology, chemical and crystalline characteristics, microstructure, and porosity of CNFs in the aerogels were not affected by the addition of NH 4 Cl.
This study examines the suspension stability of iron oxide nanoparticles of different sizes, magn... more This study examines the suspension stability of iron oxide nanoparticles of different sizes, magnetic susceptibility, and saturation magnetization over long time scales in dilute systems using timeresolved UV-visible spectroscopy. The effects of citric acid as a chelating agent and applied external magnetic field are also studied. UV-visible spectra are obtained at different times for citric-acid-stabilized nanoparticles dispersed in water, and the peak absorbance is tracked with time, in the presence and absence of external magnetic fields. It is seen that the nanoparticles sediment slowly even in the absence of chain formation, with the phenomenon occurring in two-to-three regimes for the systems studied. Sedimentation exhibits either exponential or powerlaw behavior of maximum absorbance with time. In the dilute dispersions studied, thermal dispersion is about two orders of magnitude stronger than van der Waals interactions, and chain formation is not easy. Yet, it is likely that local anisotropic structures of the nanoparticles form, through which the attractive interactions result in sedimentation. Citric acid gradually stabilizes the aggregating particles; after an initial faster sedimentation, electrostatic repulsion causes the particles to segregate, as observed by a linear increase in the concentration of the nanoparticles at long times. In the presence of magnetic field, stabilization effects are significantly reduced. It is seen that though the attractive force between the nanoparticles and the external field is smaller than Brownian forces, together with van der Waals interactions, these Electronic supplementary material The online version of this article (
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